Genome copy number predicts extreme evolutionary rate variation in plant mitochondrial DNA.

Nuclear and organellar genomes can evolve at vastly different rates despite occupying the same cell. In most bilaterian animals, mitochondrial DNA (mtDNA) evolves faster than nuclear DNA, whereas this trend is generally reversed in plants. However, in some exceptional angiosperm clades, mtDNA substitution rates have increased up to 5,000-fold compared with closely related lineages.

Disentangling Positive Selection from Relaxed Selection in Animal Mitochondrial Genomes.

AbstractDisentangling different types of selection is a common goal in molecular evolution. Elevated / ratios (the ratio of nonsynonymous to synonymous substitution rates) in focal lineages are often interpreted as signs of positive selection. Paradoxically, relaxed purifying selection can also result in elevated / ratios, but tests to distinguish these two causes are seldomly implemented.